1. Field of the Invention
The present invention relates to a thermoplastic elastomer composition for powder molding, powder, a powder molding method and a molded article. More specifically, the present invention relates to a thermoplastic elastomer composition for powder molding which comprises a polyolefin-based resin and a hydrogenated diene-based copolymer having a specific structure as essential components, and which can provide a molded article that is not easily whitened on bending, and does not generate gloss when heated at temperatures from about 80xc2x0 C. to less than the melting point of the polyolefin-based resin; a powder composed of said composition; a powder molding method using said powder; a molded article obtained by powder-molding said powder; and a multi-layer molded article using said molded article.
2. Description of the Related Arts
Conventionally, molded articles in the form of a sheet having on the surface complicated uneven patterns such as leather grains, stitches and the like are used as skin materials of automobile interior parts or the like. As such molded articles, there have been proposed molded articles obtained by powder molding of a powder which is produced by pulverizing an olefin-based thermoplastic elastomer, for replacing conventional molded articles of vinyl chloride-based resins (see, e.g., JP-A-05-1183 and JP-A-05-5050). However, a molded article obtained by such a method is harder and has a property that it is easily whitened on bending, as compared with vinyl chloride-based resin molded articles, therefore, there was a tendency that the bent portion was whitened to cause appearance failure when the molded article was released from a mold after production and when the molded article was molded into intended form, and the like. Further, JP-A-07-82443 discloses a powder resin composition composed of a polyolefin-based resin and a hydrogenated styrene-butadiene rubber having a styrene content of 20% by weight or less, and JP-A-03-72512 discloses a thermoplastic elastomer composition composed of a non-polar resin such as polypropylene or the like, and a hydrogenated diene-based copolymer having a specific structure.
A molded article obtained by powder molding of these powder resin compositions had a problem that when used as an automobile interior material, appearance failure occurs, since the molded article reveals gloss when heated at a temperatures from about 80xc2x0 C. to less than the melting point of the polyolefin-based resin (it is known that when an automobile is left outdoor in summer, temperature of the surface of automobile interior materials such as an instrument panel reaches up to about 80 to 120xc2x0 C.) though when the molded article is bent, the bent portion is not whitened.
Two-layer molded articles constituted of a skin layer composed of a vinyl chloride-based resin and a foamed layer composed of a polyurethane-based resin are widely used for automobile interior parts such as an instrument panel, console box, door trim and the like. Recently, there is an effort to unify a skin layer and a foamed layer into a thermoplastic elastomer composition material from viewpoints of recycle and the like, however, there has not been known a two-layer molded article in which both of a skin layer and a foamed layer are composed of a thermoplastic elastomer composition, and which is not whitened on bending, does not reveal gloss when heated at temperatures from about 80xc2x0 C. to less the melting point of the polyolefin-based resin, and has excellent cushioning property.
An object of the present invention is to provide a thermoplastic elastomer composition for powder molding which comprises a polyolefin-based resin and a hydrogenated diene-based copolymer having a specific structure as essential components, and which can provide a molded article that is excellent in flexibility, is not easily whitened on bending in the bent portion, and further, does not generate gloss when heated at temperatures from about 80xc2x0 C. to less than the melting point of the polyolefin-based resin, a powder composed of said composition and a powder molding method using said powder.
Another object of the present invention is to provide a molded article obtained by powder-molding this powder and a two-layer or multi-layer (three or more layer) molded article using this molded article.
Still another object of the present invention is to provide a two-layer or multi-layer molded article having an excellent cushioning property in addition to the above-descried properties, comprising the above-mentioned molded article as a skin layer and a foamed layer composed of a thermoplastic elastomer composition containing a polyolefin-based resin and a rubbery polymer having a specific structure.
Other objects and advantages of the present invention will be apparent from descriptions below.
Namely, the present invention relates to a thermoplastic elastomer composition for powder molding comprising 100 parts by weight of the following component (A) and 10 to 1000 parts by weigh of the following component (B), wherein the complex dynamic viscosity xcex7*(1) at 250xc2x0 C. is 1.5xc3x97105 poise or less, and the Newtonian viscosity index n is 0.67 or less:
(A): a polyolefin-based resin,
(B): a hydrogenated diene-based copolymer satisfying all of the following conditions ({circle around (1)} to {circle around (7)}),
{circle around (1)}: the hydrogenated diene-based copolymer contains the following structural units (a) and (b):
(a): a vinyl aromatic compound polymer block,
(b): at least one block selected from the group consisting of following (b1), (b2) and (b3):
(b1): a block obtained by hydrogenation of a random copolymer block composed of a vinyl aromatic compound and a conjugated diene,
(b2): a block obtained by hydrogenation of a tapered copolymer block composed of a vinyl aromatic compound and a conjugated diene in which the amount of the vinyl aromatic compound increases gradually,
(b3): a block obtained by hydrogenation of a conjugated diene polymer block,
{circle around (2)}: the total content(T: percentage) of vinyl aromatic compound units contained in the hydrogenated diene-based copolymer is from 10 to 18% by weight,
{circle around (3)}: the ratio (S: percentage) of the content of the vinyl aromatic compound unit of (a) in {circle around (1)} to the total content of vinyl aromatic compound units contained in the hydrogenated diene-based copolymer is 3% or more,
{circle around (4)}: the ratio (V: percentage) of the number of hydrogenated conjugated diene units having a side chain of two or more carbon atoms to the total number of hydrogenated conjugated diene units in the hydrogenated diene-based copolymer is over 60%,
{circle around (5)}: (T) in {circle around (2)}, (S) in {circle around (3)} and (V) in {circle around (4)} in the hydrogenated diene-based copolymer satisfy the relation represented by the following expression (1):
Vxe2x89xa60.375xc3x97S+1.25xc3x97T+40xe2x80x83xe2x80x83(1)
{circle around (6)}: 80% or more of double bonds derived from conjugated diene units in the hydrogenated diene-based copolymer are hydrogenated, and
{circle around (7)}: the number average molecular weight of the hydrogenated diene-based copolymer is from 50000 to 400000.
Further, the present invention relates to a powder of the above-mentioned thermoplastic elastomer composition for powder molding and a powder molding method using said powder.
Furthermore, the present invention relates to a molded article obtained by powder-molding the powder, and a two-layer or multi-layer molded article containing said molded article and a method for producing the same.
Still further, the present invention relates to a two-layer molded article comprising (I) a layer of the above-mentioned thermoplastic elastomer composition for powder molding and (II) a layer described below:
(II): a foamed layer composed of a thermoplastic elastomer composition containing 100 parts by weight of the following component (G) and 10 to 1000 parts by weight of the following component (H):
(G): a polyolefin-based resin,
(H): a rubbery polymer wherein in tan xcex4-temperature-dependence curve obtained by measuring solid viscoelasticity of a composition prepared by kneading with (G), a new single tan xcex4 peak is given at a temperature different from both of the tan xcex4 peak temperature of (G) and the tan xcex4 peak temperature of (H), in a temperature range from xe2x88x9270 to 30xc2x0 C.
Also, the present invention relates to a multi-layer molded article in which a thermoplastic core material is laminated on the side of the layer (II) of the two-layer molded article, and a method for producing the same.